In foundry operations, molten metal is often cast in a sand mold. To retain the shape of the mold, the sand may be treated with a resin binder, and may include imbedded metal reinforcing cores or rods for additional strength. To reduce costs, it is beneficial to reclaim the sand for reuse in subsequent molding operations.
Various types of sand reclaiming devices and methods are generally known in the art. For example, U.S. Pat. No. 4,025,419 to Musschoot and U.S. Pat. No. 4,415,444 to Guptail, which have a common assignee as the present invention, disclose vibratory sand reclaiming apparatus. In these patents, sand lumps are introduced into a vibrating chamber where they are agitated and abrade each other to produce discrete sand particles. A pair of motors having eccentrically loaded shafts are attached to the chamber and operated in opposite directions to generate a vibratory agitating motion. Sand grains freed from the clumps pass through an exit screen to be collected for reuse.
In addition to the lumps of used foundry sand, additional included material, such as metal rods, cores, or other irreducible material, may also be deposited into the chamber. Over time, the included material accumulates in the chamber and must be removed. Accordingly, the previously known sand reclaiming devices include a third motor attached to the chamber which, when operated simultaneously with one of the other two motors, generates a vibratory motion in a reverse direction toward a reject outlet. As a result, the included material may be discharged from the chamber. While the devices described in the '419 and '444 patents reduce sand lumps in a satisfactory manner and allow for easy removal of included materials, they are overly complex and expensive to build.
Prior vibratory sand reclamation devices also include overly costly gates to close off the reject outlet during normal operation. Such gates typically include a seal for tightly closing off the outlet. The seals, however, are subject to wear and therefore deteriorate quickly, necessitating frequent replacement. In addition, the gates often include an actuator, such as a pneumatic cylinder, and linkage for moving the gate between open and closed positions. The actuator and linkage, however, increase the complexity and cost of the device.